Emitter tube for irrigation system

ABSTRACT

The invention provides an emitter tube for an irrigation system, the tube being of resiliently flexible material having a base inlet end adapted to be mounted and a free outlet end adapted to be unmounted, the arrangement being such that, with liquid flowing at a sufficient rate through the emitter tube, hydraulic forces exerted by the flowing liquid on the tube cause the outlet end continuously to move about, further having a base section and an end section downstream from the base section when the end section is of greater flexibility than the base section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

THIS invention relates to an emitter tube suitable for an irrigationsystem.

2. Description of Related Art

The Applicant's U.S. Pat. No. 4,915,312 discloses an irrigation systemwhich includes a sprinker device for liquids comprises an emitter tubeof resiliently flexible material having a base inlet end adapted to bemounted and a free outlet end adapted to be un-mounted, the arrangementbeing such that, with liquid flowing at a sufficient rate through theemitter tube, hydraulic forces exerted by the flowing liquid on the tubecause the outlet end continuously to move about. The emitter tube ismounted on a fitting which has a flow passage there through which leadsinto the emitter tube, the flow passage having, at its inlet end, a pairof grooves which lead tangentially into the flow passage. Thesetangentially arranged grooves impart a swirling motion to water enteringthe emitter tube. A pop-up sprinkler is also disclosed in which theemitter tube is mounted on a plunger which is displaceable in a barrel,the emitter tube protruding through an opening at the end of the barrel.

This system is further disclosed in the Applicant's U.S. Pat. No.4,856,552 which relates to a flow regulating device suitable for use inthe above system.

The specifications of these U.S.A. patents are incorporated into thisspecification by way of reference. It has been found that the emittertube which is disclosed in the above United States patents, lends itselfto advantageous modifications for certain applications.

For example, in certain applications a greater radius of throw ofirrigation water is desirable and it has been found that the emittertube can be modified to achieve such a results.

Also for example a more even water distribution with a single sprinkleras well as water distribution with sprinklers laid out on the standardgroup spacing could be achieved by modifying the emitter tube. Furtherfor example where the size of the droplets of irrigation water is to becontrolled, the emitter tube could likewise be modified to achieve sucha result.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a novelemitter tube of the type disclosed in the above United States patentswherein the frequency of oscillation of the tube in use is reduced for agiven specific flow rate.

A further object of the invention is to provide an emitter tube having agreater radius of throw of irrigation water.

A further object of the invention is to provide a sprinkler systemhaving an improved distribution with a single sprinkler, as well as animproved water distribution with sprinklers laid out on standard gridspacings.

A further object of the invention is to provide an emitter tube which iscapable of producing droplets of irrigation liquid of a controlled size.

A resiliently flexible emitter tube of the type described in U.S. Pat.No. 4,915,312 having a base section and an end section downstream fromthe base section wherein the end section is of greater flexibility thanthe base section.

In one arrangement the emitter tube is characterized in that a basesection of the emitter tube has a wall thickness which is greater thanthe end section of the tube. Preferably the wall thickness of the tubewill taper evenly from the base thereof towards the free end thereof.Alternatively, the wall thickness of the emitter tube could be steppedat one or more intervals along its length so as progressively to reducein wall thickness.

In a further embodiment of the invention the emitter tube will comprisean end section, an intermediate section and a base section, and thearrangement will be one wherein the intermediate section is of greaterflexibility than the base section and the end section is in turn ofgreater flexibility than the intermediate section. In this arrangementthe intermediate section could thus define a waist portion of reduceddiameter.

In one embodiment in accordance with the invention the inner diameter ofthe tube could remain substantially constant, while the outer profile ofthe tube will reduce in wall thickness from the base thereof towards thefree end thereof.

Thus in one example where the tube has length of 177 mm, the outerdiameter thereof at the base could be 10 mm, and the outer diameterthereof at the free end could be 6 mm, with the tube tapering evenlybetween the base and free end. The inner diameter of the tube could be 5mm in the above case. These dimensions could vary widely and theinvention is in no way limited in this regard.

A further alternative provides for the inner passage of the tube totaper outwardly from a larger diameter at the base to a smaller diameterat the end thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

A further features of the invention will appear from the preferredembodiment which is described below purely by way of example withreference to the accompanying drawing wherein:

FIG. 1 is a schematic sectioned elevation of an emitter tube arrangementin accordance with the invention;

FIG. 2 is a schematic sectioned elevation of an irrigation leadincluding the emitter tube of FIG. 1; and

FIG. 3 is a schematic section elevation of a different embodiment of theemitter tube in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

U.S. Pat. No. 4,915,312 which is referred to above and discloses anirrigation system which includes a sprinkling device for liquidscomprises an emitter tube 10 of resiliently flexible material having amounted base 10 a and an unmounted outlet end 10 b, the arrangementbeing such that, with liquid flowing at a sufficient rate through theemitter tube 10, hydraulic forces exerted by the flowing liquid on thetube cause the outlet end 10 b continuously to move about. The emittertube is mounted on a fitting which has a flow passage there throughwhich leads into the emitter tube, the flow passage having, at its inletend, a pair of grooves which lead tangentially into the flow passage.These tangentially arranged grooves impart a swirling motion to waterentering the emitter tube. A pop-up sprinkler is also disclosed in whichthe emitter tube is mounted on a plunger which is displaceable in abarrel, the emitter tube protruding through an opening at the end of thebarrel.

The emitter tube 10 is designed to perform a whiplash-type of action invertical planes while rotating about its vertical axis. The tube 10 willthus move to and fro in a vertical plane which is continually rotatingas a result of rotational action of the water stream within the tube 10.The emitter tube 10 of the present invention is designed to operate withan increased internal water pressure, and thus velocity while limitingthe frequency of the oscillating to and fro whiplash-type movements ofthe emitter tube 10. In this way, a greater distance of throw isobtained with the emitter tube 10 of the invention relative to a priorart emitter tube as disclosed in the above United States patent.

With reference to the drawings, the current invention teaches an emittertube 10 for use in such irrigation systems which is characterised inthat a base zone 10 a of the emitter tube 10 is provided with a greaterwall thickness than the tube 10 towards the free end 10 b thereof. Thusin the arrangement illustrated, the wall thickness of the emitter tube10 tapers evenly from a relatively thick base zone 10 a to a relativelythin free end 10 b.

The above arrangement results in less flexibility at the base section 10a of the tube to permit the use of higher irrigation water pressures,without an increase in the frequency of oscillation of the tube 10 inuse.

In the arrangement shown, the inner diameter of the tube remainsconstant while the outer profile is tapered as described above. In thiscase, the total length the tube is 177 mm, and the wall thickness at thebase 10 a thereof is in the order of 3 mm, and tapers evenly to a wallthickness at the extremity of the tube which is in the order of 0.5 mm.It has been found that many variations of the arrangement above arepossible. For example, in certain instances, not shown, the insidediameter of the tube 10 could taper from a relatively large diameter atthe base thereof to a smaller diameter at the free end thereof, whilethe outer profile of the tube could be of constant wall thickness, oralso tapered to provide a desired result.

In a further alternative, not shown, the tube 10 could be stepped atintervals along its length so as to reduce in wall thickness from thebase 10 a to the free end 10 b thereof.

In a further alternative arrangement shown schematically in FIG. 3,wherein an intermediate section 10 c of the tube which is disposedbetween the end section 10 b and the base section 10 a of the tube 10 isprovided with a reduced wall thickness. This renders the intermediatesection 10 c of the tube more flexible to induce flexing of the tube inthis section 10 c in use. The end section 10 b of the tube will likewisebe flexible to perform a whiplash-type of action during oscillation ofthe tube 10. This tube therefore mimics the actual whiplash-type ofmovement of a prior art tube, in a controlled fashion. Thus the lengthand flexibility of the intermediate section 10 c and the end section 10b can be pre-selected to give a predetermined performance. For exampleby varying the flexibility of the intermediate section 10 c, thefrequency of oscillation can be varied.

It has been found that with the tube 10 described above, one or more ofthe following benefits will accrue:

-   1. An increased radius of throw has been experienced with a more    uniform water distribution. It has been found that because the    emitter tube 10 is relatively rigid, it resists flexing thus    reducing oscillating speed and maintaining larger droplet sizes for    a further throw of irrigation water.-   2. With such an increase in the radius of throw, a reduction of the    infield infrastructure accrues and results in a reduction in the    cost of this system.-   3. The expected improved distribution renders the use of the    sprinkler head shown in FIG. 2, possible on a low riser.-   4. The wall thickness of the tube 10 minimizes the possibility of    blow-outs caused by excess air during the start up of this system. A    blow out normally occurs when there is excessive air in the system    that cannot escape fast enough and the tube 10 is then inflated    causing damage thereto.-   5. The expected increase in the radius of throw allows for wider    spacings on low risers further reducing costs. In a irrigation    system, the spacings between irrigation heads, FIG. 2, of 12×12    meters or 12×14 meters on a low riser (60 to 90 cm) are possible.    The spacings of 15×15 meters on tall risers could be achieved.-   6. Reduction in labour costs results due to the fact that less    equipment is required to be moved during the harvest of some crops.-   7. A reduction in labour cost also results due to the fact that less    equipment may be required to be moved on a movable system.-   8. New applications for the sprinkler shown in FIG. 2 are possible,    for example used as Side rolls on irrigation machines.-   9. A system utilising the emitter in FIG. 1 should exhibit better    wind resistance due to larger droplets with a higher velocity.-   10. With the emitter tube in FIG. 1, a curved droplet trajectory is    achieved reducing dry areas behind obstacles such as trees.

Clearly many variations of the tube are possible as mentioned abovewithout departing from the principles set out in the consistory clauses.

1. An emitter tube suitable for an irrigation system, said tube formedfrom a resiliently flexible material including a base inlet end adaptedto be mounted and a free outlet end adapted to be un-mounted, said tubefurther including a base section adjacent to the base inlet end and anend section downstream from said base section, an inner diameter of theemitter tube is substantially constant, while an outer diameter of theemitter tube tapers evenly from the base section to the outlet end,wherein said end section has greater flexibility than said base section;and wherein, with a liquid flowing at a sufficient rate through saidemitter tube, hydraulic forces exerted by the flowing liquid on saidemitter tube cause said outlet end to move continuously.
 2. The emittertube according to claim 1, wherein said base section of said emittertube has a wall thickness which is greater than a wall thickness of saidend section.
 3. The emitter tube according to claim 1, furthercomprising: an intermediate section disposed between the base sectionand the end section, wherein said intermediate section is of greaterflexibility than said base section.
 4. The emitter tube according toclaim 3, wherein said end section has greater flexibility than saidintermediate section.
 5. The emitter tube according to claim 1, whereinthe outer profile of said emitter tube reduces in wall thickness fromsaid base section towards said outlet end.
 6. The emitter tube accordingto claim 1, wherein said tube has an overall length of approximately 177mm, an outer diameter at said base inlet end of approximately 10 mm, andan outer diameter at said outlet end of approximately 6 mm.
 7. Theemitter tube according to claim 6, wherein the inner diameter of saidemitter tube is an approximately constant 5 mm along the length of saidemitter tube.